Antigenic changes produced by complex formation between thrombin and antithrombin-III.
Immunization of goats and mules with human thrombin resulted in an antiserum that reacted only weakly with the parent molecule, prothrombin. Some of the antibodies in this antiserum showed a greater affinity for thrombin complexed to its naturally occurring inhibitor, antithrombin-III, than for active thrombin. An antiserum against the human thrombin inhibitor, antithrombin-III, produced 2 precipitin lines against human serum but only 1 against plasma. The 2nd line in serum was shown to represent precipitation of a complex of thrombin with antithrombin-III. The neoantigens appearing in antithrombin-III after complex formation were also present in complexes prepared with purified clotting factor Xa and antithrombin-III. Since purified host (mule) thrombin was also capable of causing formation of the neoantigenic sites when complexed to human antithrombin-III, it seems likely that these determinants result from interaction in the host between the immunogens (either human thrombin or antithrombin) and the appropriate interacting host protein (mule antithrombin-III or thrombin, respectively). Studies by radioimmunoassay showed that the antibodies formed are not completely specific for the neoantigens since they also react to a lesser extent with the free proteins.
D000818:Animals; D000936:Antigen-Antibody Complex; D000941:Antigens; D000990:Antithrombin III / Q000276:immunology*; D006041:Goats; D006801:Humans; D005779:Immunodiffusion; D010527:Perissodactyla; D011817:Rabbits; D011863:Radioimmunoassay; D011946:Receptors, Antigen; D013917:Thrombin / Q000276:immunology*
D000936:Antigen-Antibody Complex; D000941:Antigens; D011946:Receptors, Antigen; D000990:Antithrombin III; D013917:Thrombin